Hibiscus

Hibiscus include a very wide variety of plants grown not only for their ornamental flowers but also as vegetables and fiber plants. Some are hardy perennials, while others are annuals, shrubs or tropical plants. This fact sheet covers perennial and annual hibiscus, as well as closely related plants commonly grown for ornamental purposes in South Carolina.

Perennial Hibiscus

Mature Height/Spread: While dwarf varieties may only grow two to three feet tall, many varieties and species can attain heights of eight feet or more each growing season once established. Young plants are generally narrower than they are tall, but mature clumps will often spread as wide as their height.

Growth Rate: Perennial hibiscus generally reach mature height within two or three years, and return to that height each year. Best growth occurs when plants have ample moisture. Many hardy hibiscus are capable of blooming the first year from seed started in early spring.

Ornamental Features: Hibiscus are grown primarily for their strikingly beautiful and often amazingly large flowers. The foliage of many is often bold and remarkable as well, but is less noticed because the mid to late summer blossoms are so prominent. Hibiscus give a bold, tropical effect to a garden. They are also highly attractive to butterflies and hummingbirds.

Culture: Many of the perennial hibiscus are natives of South Carolina and the Southeastern US. They prefer a sunny location and well drained soil containing plenty of organic matter. These conditions result in the most vigorous growth. Hibiscus will tolerate light shade and less desirable soils, but their vigor and flowering will be reduced. Plenty of water is necessary for the most abundant blooming. Water plants deeply and thoroughly, but allow some time between drenchings on established plants. Newly planted hibiscus will need more frequent watering, like other newly planted perennials. Some species and varieties will actually tolerate permanently damp soil and flooding.

Tall hibiscus should be sited where they are not exposed to strong winds to avoid breaking of the long stems. Stems that break can be shortened and new side shoots will grow and produce more blooms.

To encourage rebloom, either remove old flowers before they form seedheads or prune plants back by one third after a flush of bloom is finished.

Perennial hibiscus will freeze back to the ground each winter in all but the warmest parts of South Carolina. Old stems can then be cut back to the ground. New shoots emerge by mid spring.

Propagation: Hibiscus are easy to propagate by several methods, making them a common passalong plant, especially since some popular types such as Confederate Rose can be difficult to find in stores.

Cuttings: Cuttings can be rooted at anytime that new growth is available, although rooting is usually quickest in spring. Start with pencil thick, five to six inch long cuttings of firm new growth. Strip off lower leaves and insert the cutting in a mix of three parts sand and one part peat. Roots should form within four to five weeks. Once roots are formed plants can be moved into a larger container or transplanted to a permanent location.

Seeds: Seed can be sown indoors 12 weeks before the last spring frost. Soak seeds in very warm water for one hour before sowing. Seed can also be sown in place outdoors after the last expected frost date or fresh seed can be sown in fall. Collect seed for fall sowing once the papery seed capsules brown and start to split. Plants often bloom from seed in their first year and will often self seed in suitable soil conditions.

Division: Perennial hibiscus can be divided in spring. Be careful working around the soft new shoots. They do not usually tolerate fall division or transplanting.

Problems: Leaf spots may be caused by several fungi. In most cases, cleaning up plant debris and removing infected leaves will provide adequate control. Southern stem blight may occur on hibiscus. To help prevent southern blight, keep mulch from touching the stems.

Insect pests of hibiscus include aphids, whiteflies, and Japanese beetles.

Species & Cultivars

Scarlet Swamp Hibiscus (Hibiscus coccineus): This southeastern native hibiscus also commonly known as Texas Star. The six to eight inch wide flowers are brilliant red, with petals more separated than those of other hibiscus, giving the blossom a star shaped look. Individual flowers last only a day but new blooms open throughout summer and fall. The leaves are deeply divided into narrow, toothed, finger-like lobes. This plant is often passed along from gardener to gardener.

Established plants grow to seven feet each growing season. Plants die back to ground level in winter and resprout in spring.

Scarlet swamp hibiscus prefers full sun and moist soil. Naturally occurring in swamps, marshes and ditches, this hibiscus will even tolerate some flooding, although it will also thrive in ordinary garden soil.

Divide plants in spring. Plants often self seed from seeds produced in fall.

Rose Mallow (Hibiscus moscheutos): Rose mallow is native to marshy areas throughout the southeast. It has been extensively bred and is the parent of a number of popular hibiscus hybrids, often referred to as dinner plate hibiscus due to the large size of their flowers. The large, fast-growing plants bloom from August to October. Individual flowers last only a day, but each plant may flaunt several 10 to 12 inch wide flowers at once.

Grow rose mallows in rich, well-drained soil with full sun for best results. At the end of autumn, cut old stems back to three to six inches above ground level.

Propagation is possible from seed, tip cuttings and root division. Rose mallows will flower from seed the first year if started very early in spring. Favorite cultivars may be rooted from cuttings during the growing season.

'Turn of the Century' is a newer variety. The flowers are pink with a red center. Because the petals are deeper colored on one side, the blossoms have a pinwheel effect. Plants grow up to six to eight feet tall.

Confederate Roses (Hibiscus mutabilis): These large shrubs grown as very tall perennials in most of the state. Near the coast they will leaf out on old stems, but in most areas, the tops will die back and the plant will regrow each spring from the base. Oddly enough, Confederate roses are not native to the South but come from China. They thrive in the South anywhere that they have time to open their very late flowers before fall frost. This species is a popular passalong plant.

Height varies from about eight feet in the upstate to up to 15 feet on the coast.

There are several color forms, including one commonly called Blood on the Rose, which opens white and changes to a deep pink that is almost red by the second day after opening. A double pink type is also common, but double white, and single pinks and whites are also seen. The four to six inch wide flowers open in September or October. Confederate Rose is an eye-catching foliage plant even before bloom, with large, soft, gray-green leaves.

Confederate Roses are often rooted in damp sand during winter cuttings taken in fall. Cuttings 12 to 18 inches long are very easy to root in a bucket of damp sand, stored in a cool, but not freezing area such as a garage through the winter. Success rates may be even higher from spring taken cuttings.

Great Rose Mallow (Hibiscus grandiflorus): Large, felty grey leaves on eight foot stalks, topped with 10 inch wide, light pink flowers in late summer. Like those of the scarlet swamp hibiscus, flower petals do not overlap. It is native to brackish wetlands in the Southeast, and can be grown where other plants succumb to salty soil.

Annual Hibiscus

The two hibiscus most commonly grown as annuals are not true annuals, but tropical shrubs that thrive outdoors during hot South Carolina summers. They are grown as container plants.

Chinese Hibiscus (Hibiscus rosa-sinensis): This tropical shrub that is often grown outdoors in the summer and as a houseplant in winter. It is not hardy in any part of South Carolina, but can be brought inside to a bright, sunlit area for the winter and planted out each spring. Chinese hibiscus are ideal for use as seasonal container plants.

The flowers are available in many colors, ranging through the entire spectrum except blue. The yellow, apricot and orange varieties provide colors not seen in hardy perennial hibiscus. Flowers are typically four to eight inches wide, and may be single or double.

Move Chinese hibiscus outside after all danger of frost is past. Be sure to acclimate plants gradually to the increased light and lower temperatures outside. They prefer rich, well drained soil with plenty of organic matter, in full sun or light afternoon shade. Water the plants freely during the growing season, and fertilize with either a time release fertilizer every eight weeks or with a water soluble fertilizer every two weeks. To keep mature plants growing vigorously prune old wood back by about one third in spring.

Red Leaf Hibiscus (Hibiscus acetosella): The most commonly seen cultivar is 'Red Shield'. This hibiscus is a tropical shrub, grown as an annual for the beauty of its deep burgundy red, maple like leaves. It can reach five feet tall by the end of summer. Purple flowers may appear late in the growing season. Plant outside after danger of spring frost, in full sun in well drained, moist garden soil. Propagation is mainly through seed planted in the spring.

Flower of an Hour (Hibiscus trionum): This true annual that is more a curiosity than a truly ornamental plant. It grows about two feet tall, with two inch wide, white to pale yellow blooms with dark centers. The flowers close in shade and typically bloom for only a fraction of a day. It is easily grown from seed, and may self-sow and return each year, sometimes to the point of weediness.

Related Plants

There are many ornamental plants closely related and similar in appearance to hibiscus. These include hollyhocks (Alcea), mallows (Malva and Kosteletzkya species) and okra (Abelmoschus esculentus).

Hollyhock (Alcea rosea): Hollyhock is one of the most popular old-fashioned cottage garden flowers, with a distinctive upright pillar of large, brightly colored blooms for a few short weeks in summer. Hollyhocks are biennials, with young plants appearing from seed in late summer or fall and blooming the following summer.

Plants typically grow from three to six feet tall, but eight foot tall giants are not unusual, especially if grown in rich, well drained soil with ample moisture. Flowers range from three to five inches wide, and come in a full spectrum of colors.

Hollyhock rust is the main problem affecting these plants. Removing infected leaves and cleaning out old plant debris will help prevent over-wintering spores from infesting the next year's plants. Newer varieties are less susceptible to rust.

Plant hollyhocks from seeds or plants in late summer or fall. If using your own collected seed, sow it as soon as it is ripe.

Seashore Mallow (Kosteletzkya virginica): This perennial hibiscus is native to salty or brackish marshes all along the eastern seaboard. It is a useful plant near the beach, but also thrives in ordinary garden soil if given adequate irrigation. Plant in full sun.

Small, 2½ inch wide lavender-pink blossoms appear in abundance from June through October. The variety 'Immaculate' bears pure white flowers. Plants grow three to six feet tall depending on the amount of soil moisture.

Common Mallow (Malva sylvestris): This plant generally behaves as a biennial in the southeast, with young plants appearing from seed in late summer or fall and blooming the following summer. It looks much like a miniature hollyhock with 1½ to two inch wide flowers in shades of purple or lavender. Plants are variable in height, reaching anywhere from two to five feet tall. Many varieties are available from seed. The most commonly seen is 'Zebrinus', with flower petals striped purple and white. Common mallow is a native of Europe, but has become naturalized in much of the US. It readily self seeds. Plants perform best in the Piedmont, and prefer full sun, and good garden soil.

Turk's Cap (Malvaviscus arboreus): This perennial is grown for its constant blooms that resemble a Turkish turban. The bright red, three inch long hibiscus-like flowers never fully open. It is hardy near the coast in South Carolina, but may survive farther inland with a thick, airy winter mulch. Turk's Cap can easily be planted from cuttings or seed, but is not frequently found in nurseries. It is usually passed along from gardener to gardener.

Okra (Abelmoschus esculentus): Okra is a surprisingly (for anyone who has not grown it) ornamental vegetable. Like other relatives, it has a typical showy hibiscus type flower - light yellow with a dark burgundy center. The purple leafed varieties are especially attractive as focal points or as a backdrop in flower borders. Okra is an annual and is grown from seed sown after the soil has thoroughly warmed in spring.

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